function Ajax($method,$url,$parmas){
    //使用Promise
    return new Promise(function(resolve,reject){
        let xhr = new XMLHttpRequest();
        let str = "?"
        for(let key in $parmas){
            str += `${key}=${$parmas[key]}&`
        }

        if($method.toUpperCase() === "GET"){
            xhr.open($method,$url + str.slice(0,-1));
            xhr.send()
        }else{
            xhr.open($method,$url)
            xhr.setRequestHeader("Content-type","application/json")
            xhr.send(JSON.stringify($parmas))
        }

        xhr.addEventListener("readystatechange",function(){
            if(xhr.readyState === 4){
                if(xhr.status === 200){
                    //返回成功
                    resolve(JSON.parse(xhr.response))
                }else{
                    //返回错误
                    reject(JSON.parse(xhr.response))
                }
            }
        })
    })
}